The invention is a method for the autostereoscopic representation of images on a screen, for which the image information for the right eye and the left eye of a viewer is represented segmentally interleaved on the screen and a barrier is disposed, so that, for each eye, only the image information, associated with it is visible.
Such methods are used, for example, to represent a seemingly three-dimensional picture on the computer screen to the user of a computer.
The basic principle of the autostereoscopic representation of images consists of representing partial images, which in each case show the same object from different viewing directions, on the screen either simultaneously (space division multiplex) or time-offset with a rapid sequence of changing images (time division multiplex) and which in each case are visible only when the screen is viewed from an appropriate viewing direction. If the image is viewed only by a single user from a fixed viewing position, it is sufficient to show two half images, which correspond to the image information for the left eye and the right eye.
In the case of some known systems, the image information for the left eye and the right eye is separated with the help of suitable spectacles, such as shutter spectacles or polarization spectacles. However, these systems have the disadvantage that the user is affected by wearing these spectacles. On the other hand, autostereoscopic methods or devices have the advantage that the spatial impression can be perceived with the "unarmed eye". In this case, a so-called parallax barrier, referred to in the following in abbreviated fashion as "barrier", ensures that the half image intended for the right eye, is invisible for the left and vice versa. The barrier can be formed, for example, by a lens raster or prism raster or by an aperture raster, which is disposed before the screen. Under some circumstances, such as in the case of transmitted light LCD screens or in the case of a rear projection screen, the aperture raster can also be disposed behind the screen.
In the case of known autostereoscopic methods, for which a raster screen with a particular pixel raster is used as a screen, such as is the case, for example, with conventional cathode ray picture tubes or liquid crystal (LCD) screens, and for which the half images for the right eye and for the left eye are interleaved segmentally with one another, the segments generally have the width of a single screen pixel. Thus, if the pixels of a screen cell are numbered consecutively, all odd-numbered pixels, for example, form the half image for the left eye and all even-numbered pixels, the half image for the right eye. These known systems react basically very sensitively to changes in the viewing position. If the user moves his head only slightly to the side or if the viewing distance is changed slightly, the correct allocation between the screen pixels and the eyes of the viewer and, with that, the three-dimensional impression of the image is also lost.
The DE 195 00 699 A1 discloses a method of the type named above, for which the viewing position is monitored continuously with the help of a head or eye tracking system and, in the event of a change in the viewing position, the barrier is adjusted automatically. For example, in the case of a barrier, constructed as prism raster, the adjustment takes place owing to the fact that the barrier is moved mechanically. If the barrier is formed by a line shadow raster LCD, the adjustment can also be made electronically by suitably triggering this LCD. However, in the case of this known method also, a high precision is required for the configuration and adjustment of the barrier, so that a clean channel separation is achieved. A particular problem consists therein that, in the case of most of the computer screens customary at the present time, especially in the case of cathode ray picture tubes, the screen surface is not completely flat, but curved slightly. This results in distortions, which can hardly be controlled by appropriately adapting the barrier. A further problem consists in that the head or eye tracking system and the adjusting system for the barrier, which is connected in series, operate with a certain delay so that the quality of the threedimensional picture reproduction cannot be maintained permanently if the viewer moves.
In Applicant's international patent application with earlier priority, later published as WO98/53616, a method is already proposed for which the mutually interleaved segments on the screen each have a width of several pixels. This has the advantage that, when the channel separation is not exact, only the pixels at the edges of the segments are affected by cross talk, so that, over all, a larger tolerance for change in the position of the viewer is achieved. In addition, the possibility exists of compensating for changes in the viewing distance very rapidly and without mechanically movable parts owing to the fact that the width of the segments is adapted correspondingly. Likewise, by a suitable selection of the width of the segments, it is also possible to compensate for effects caused by the curvature of the screen. From this, the advantageous possibility arises of retrofitting existing computer screens inexpensively with an autostereoscopic device.
In the aforementioned older application, it is also already proposed that the width of the segments, invisible to the eye be enlarged at the expense of the width of the visible segments, in order to achieve a certain "safety distance" in this way and, with that, a clean separation of the channels.